JPH04127831A - Snubber circuit - Google Patents

Abstract

PURPOSE:To regenerate the energy, too, being accumulated not only in a capacitor but also in an anode reactor by providing a series circuit composed of an auxiliary semiconductor element, which is controlled synchronously with a semiconductor element, an auxiliary reactor for protecting this auxiliary semiconductor element, and the primary winding of a transformer, in the path for discharging the energy of an anode reactor. CONSTITUTION:When the voltage of a capacitor 1A is charged over the specified voltage at a time t2, by the energy accumulated in an anode reactor 8A, a regenerated current I9 begins to flow to the energy discharge path comprised of an anode reactor 8B, an auxiliary reactor 10, the primary winding of a transformer 3, an auxiliary semiconductor element 9, and an anode reactor 8A. By this regenerated current I9, the energy accumulated in the anode reactor 8A is regenerated into a DC current through a transformer 3 and a diode 7. Hereby, the energy accumulated in a series snubber circuit, that is, the anode reactor can also be regenerated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to overvoltage applied to semiconductor elements of a power converter, rate of increase in voltage (dv/dt), and rate of increase in current (dv/dt).
Regarding the snubber circuit for suppressing (di/dt), we aim to regenerate the energy stored in the Anno 7 reactor via the transformer, achieve high efficiency of the power conversion device, and reset the transformer. The present invention relates to a snubber circuit that enables high-speed switching of semiconductor elements by performing reliable switching.

[Prior Art] Generally, in a power conversion device using a semiconductor element such as a GTO, a snubber circuit is provided as a protection circuit to prevent the semiconductor element from being destroyed by overvoltage or a voltage that rises quickly.

This type of snubber circuit includes a parallel snubber circuit (consisting of a diode and a capacitor) that suppresses the rate of increase (dv/dt) of the voltage applied to the semiconductor element, and a parallel snubber circuit (consisting of a diode and a capacitor) that suppresses the rate of increase (dv/dt) of the voltage applied to the semiconductor element. There is a series snubber circuit (consisting of an anode reactor) that suppresses /clt>.

Conventionally, with the increase in the capacity of power conversion bags W, a technology has been proposed in which energy stored in a capacitor, which is a component of a parallel snubber circuit, is regenerated into a power supply etc. via a transformer, with the aim of improving efficiency. ing.

FIG. 7 is a circuit diagram showing a power conversion device (for example, for one arm of an inverter) using a conventional snubber circuit, as described in, for example, Japanese Patent Laid-Open No. 63-213411.

In the figure, a capacitor (1^) and a diode (2^)
and transformer (3^) constitute a parallel snubber circuit A, and the capacitor (IB), diode (2B) and transformer (3B
) constitutes a parallel snubber circuit B. The parallel snubber circuits A and B each have the same configuration, and are connected in parallel to a pair of semiconductor elements (4^) and (4B) inserted in series between the DC bus bars of the power converter. .

In this case, the semiconductor elements (4^) and (4B) are GTO
(gate turn-off thyristor), and is a half-bridge that constitutes a power conversion device.

In the parallel snubber circuit A, the diode (2^) is connected in the charging direction of the capacitor (1^), and the negative winding of the regenerative transformer (3^) is the discharge path of the capacitor (1^). That is, it is connected between both ends of the diode (2^), and the secondary winding of the transformer (3^) is inserted between the DC bus bars of the power converter. The parallel snubber circuit B also has a similar configuration.

Diodes (5^) and (5B) are connected in parallel to the semiconductor elements (4^) and (4B), respectively. In addition, the DC power supply (6) supplies a power supply voltage E between the DC buses, and the secondary windings of the transformers (38) and (3B) are equipped with diodes (7^) and (7B), respectively. is inserted.

In the power converter configured as described above, the semiconductor elements (4^) and (4B) alternately turn on and off, thereby generating an AC current to the load (not shown) connected to the output terminal T. It is designed to supply a load current I of . This load is usually an inductive load and has a large inductance component.

Next, the operation of the conventional snubber circuit shown in FIG. 7 will be explained.

Here, it is assumed that the load is an inductive load, the load current is flowing in the direction of the arrow in the figure, and the semiconductor element (4^)
It is assumed that the magnitude and direction of the load current I are constant during the switching operations of (4B) and (4B).

First, the commutation of the load current ■ from the semiconductor element (4^) to the diode (5B) will be explained.

Now, semiconductor element (4^) is on, semiconductor element (4B)
Assuming that is off, a load current ■ is flowing to the output terminal T via the semiconductor element (4^), and the capacitor (
The voltage of 1^) is 0, and the voltage of the capacitor (IB) is charged to the power supply voltage E.

In this state, when the semiconductor element (4^) is turned off, the load current (2) is bypassed to the diode (2^) and the capacitor (1^), and the capacitor (1^) is charged by the load current I.

Here, if the winding ratio between the secondary winding and the primary winding of the transformers (3^) and (3B) is respectively n, then the capacitor (1
When the voltage of ＾) is charged to E/n or more, the capacitor (IB) starts discharging. Also, a capacitor (1
The diode (5B) begins to conduct when the voltage of ＾) is charged above the power supply voltage E. And the capacitor (
The discharge of IB) is completed, and the voltage of the capacitor (1Δ) becomes E
When charged to +E/n, the diode (5
Load current I flows through B) and commutation is completed.

At this time, the discharge current of the capacitor (IB) is transferred to the transformer (3
B), and is regenerated to the DC power supply (6) via the secondary winding of the transformer (3B) and the diode (7B).

Also, the E/n that was overcharged in the capacitor (18)
The voltage of E is discharged and becomes steady state at power supply voltage E,
At this time, the energy stored in the capacitor (1^) as an overcharge becomes a discharge current and is transferred to the transformer (3^).
The current flows through the secondary winding of the transformer (3^) and is regenerated to the DC power supply (6) via the diode (7^).

Note that during the above commutation period, the semiconductor element (4B) is turned off, and even if the semiconductor element (4B) is turned on after the commutation period ends, the steady state remains as long as the assumption at the beginning holds true. maintained.

Next, commutation of the load current I from the diode (5B) to the semiconductor element (4^) will be explained.

First, the semiconductor element (4^) is off, the load current is flowing through the diode (5B), and the capacitor (IB
) voltage is O, and the voltage of capacitor (1^) is power supply voltage E
When the semiconductor element (4^) is turned on in a state where it is charged, the current flowing through the semiconductor element (4^) is equal to the load current I.
The current flowing through the diode (5B) becomes O.

Further, the current flowing through the semiconductor element (4^) increases, and the current equal to or higher than the load current is bypassed to the diode (2B) and the capacitor (IB), and the capacitor (IB) is charged.

Then, when the voltage of the capacitor (IB) is charged to E/n or more, the capacitor (1^) starts discharging. The capacitor (1^) has completed discharging and the capacitor (
When the voltage of IB) is charged to E + E / n, the current flowing through the semiconductor element (4^) becomes load current I.

At this time, the discharge current of the capacitor (1^) is transferred to the transformer (3)
By flowing to the negative winding of 8), the capacitor (1^
) is regenerated to the DC power supply (6) via the secondary winding of the transformer (3^) and the diode (7^). Also, the E that was overcharged in the capacitor (IB)
/n voltage is discharged, and a steady state is reached at the power supply voltage E. The energy stored in the capacitor (IB) as an overcharge becomes a discharge current and flows through the transformer (3B).
It flows to the next winding and is regenerated to the DC power supply (6) via the secondary winding of the transformer (3B) and the diode (7B). During and after this period, the semiconductor element (4B) remains turned off.

On the other hand, when the load current ■ is flowing in the opposite direction to the arrow, the diode (5^) from the semiconductor element (4B)
The commutation operation from the diode (5^) to the semiconductor element (4B) is performed by the above-mentioned semiconductor element (4B).
The operation is completely symmetrical to the OFF and ON operations of ＾).

In this way, in the conventional snubber circuit, only the energy stored in the capacitors (1^) and (IB) in the parallel snubber circuit is recovered, and the energy is stored in the series snubber circuit, that is, the anode reactor (not shown). The energy produced is
It is wasted through resistors, etc.

In addition, since the regeneration transformers (3^) and (3B) rely on self-resetting, the iron cores of the transformers (3^) and (3B) are not reset reliably and may become saturated. Therefore, if an attempt is made to prevent the saturation of the transformers (3^) and (3B), the reset time will be extended and it will be difficult to increase the frequency of the power converter. Furthermore, transformer (3^)
Since the iron cores of (3B) and (3B) cannot be used effectively, it is necessary to use an iron core with a large saturation magnetic flux density, which results in an increase in the size of the housing W.

[Problems to be Solved by the Invention] As described above, the conventional snubber circuit does not take into consideration the regeneration of the energy stored in the anode reactor, so there is a problem in that it is not possible to achieve high efficiency in the power conversion device. There was a point.

In addition, since the iron cores of the transformers (3^) and (3B) cannot be reset quickly, the minimum on-time of the semiconductor elements (4^) and (4B) becomes longer, realizing a higher frequency of the power converter. The problem was that it could not be done.

This invention was made to solve the above-mentioned problems, and it not only regenerates the energy stored in the anode reactor as well as the capacitor, but also resets the transformer quickly and reliably, and improves the efficiency of the power converter. The purpose of this invention is to obtain a snubber circuit that achieves high efficiency and high frequency.

[Means for Solving the Problems] A snubber circuit according to the present invention includes, in a discharge path of a capacitor, an auxiliary semiconductor element that is controlled in synchronization with a semiconductor element;
A series circuit consisting of an auxiliary reactor and the primary winding of the transformer is provided to protect this auxiliary semiconductor element and resonate with the capacitor, and the energy release path of the anode reactor is controlled in synchronization with the semiconductor element. A series circuit consisting of an auxiliary semiconductor element, an auxiliary reactor for protecting the auxiliary semiconductor element, and the primary winding of the transformer is provided, and the secondary winding of each transformer is inserted between the DC buses, and each A plurality of reset windings are individually magnetically coupled to the transformer, and a plurality of reset circuits are provided for exciting each reset winding in a direction that cancels out the magnetic flux of the secondary winding.

[Function] In the present invention, the energy stored not only in the capacitor in the parallel snubber circuit but also in the series snubber, that is, the anode reactor, is recovered, thereby realizing high efficiency of the power conversion device. In addition, the excitation of the reset winding cancels out the magnetic flux on the secondary winding side of the transformer and prevents saturation of the iron core.
This improves the reliability of the transformer, shortens the reset time of the transformer, and enables higher frequency power conversion equipment.

Furthermore, by applying the present invention to a power conversion device in which multiple pairs of semiconductor elements are connected in series, it is possible to increase the capacity.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a circuit diagram showing a power converter to which an embodiment of the present invention is applied.
B), (5^), (5B), (6), (7^), (7B
), T and engineering are the same as above.

The semiconductor elements (4^) and (4B) are provided with an anode reactor (8^) and (8^) as series snubber circuits, respectively.
8B) are connected in series. Here, a case is shown in which the anode reactors (8^) and (8B) are provided adjacent to each other with the output terminal T at the center.

Discharge path of capacitor (1^) in parallel snubber circuit A (
For example, between the two ends of the capacitor (1^), there is an auxiliary semiconductor element (9^) controlled in synchronization with the semiconductor element (4^) or (4B), and a second winding of the transformer (3^). A series circuit for regeneration is provided, which includes a line and an auxiliary reactor (IOA) for protecting the auxiliary semiconductor element (9^) and making it resonate with the capacitor (1^).

The auxiliary semiconductor element (9^) is, for example, a semiconductor element (4^)
It is turned on in synchronization with the on operation of , and is turned off after the regeneration operation is completed. Also, auxiliary reactor (
The inductance of 10^) is very large compared to the -order winding of transformer (3^) and also includes self-inductance, leakage inductance, or wiring inductance.

Further, the parallel snubber circuit A includes a reset winding (11^) magnetically coupled to the transformer (3^), and a reset circuit (12^) for exciting the reset winding (11^). is provided. The reset circuit (128) is
It consists of transistors (13Δ) and (14^) and diodes (15^) and (16^) of a double configuration, and is connected to a power supply for driving the reset circuit, that is, a reset power supply (17).

Similarly, the discharge path of the capacitor (IB) in the parallel snubber circuit B includes an auxiliary semiconductor element (9B) that is controlled in synchronization with the operation of the semiconductor element (4^) or (4B), and a transformer (3B). ) and an auxiliary reactor (10B) for protecting the auxiliary semiconductor element (9B) and causing resonance with the capacitor (IB). The auxiliary semiconductor element (9B) is turned on, for example, in synchronization with the off operation of the semiconductor element (4^), and
It is designed to be turned off after regeneration ends.

The parallel snubber circuit B also includes a reset winding (IIB) magnetically coupled to the transformer (3B) and a reset circuit (12B) for exciting the reset winding (11B).
and is provided. The reset circuit (12B) consists of transistors (13B) and (14B) and diodes (15B) and (16B) in a bridge configuration, and is connected to the reset power supply (17).

Furthermore, an auxiliary semiconductor element (9) controlled in synchronization with the operation of the semiconductor element (4^) and a transformer (3 ) and an auxiliary reactor (10) for protecting the auxiliary semiconductor element (9). The auxiliary semiconductor element (9) is controlled to be turned on and off in synchronization with each operation of the semiconductor element (4^) or (4B).

The secondary winding of transformer (3) is connected to other transformers (3^) and (
Similar to the secondary winding of 3B), it is inserted between the DC bus bars of the power converter, and the secondary winding has a regenerative diode (7B).
) has been inserted.

Further, the series snubber circuit including the anode reactors (8^) and (8B), the auxiliary semiconductor element (9) and the auxiliary reactor (10) includes a reset winding (11) magnetically coupled to the transformer (3). ) and a reset circuit (12) for exciting the reset winding (11) in a direction that cancels the magnetic flux of the secondary winding of the transformer (3). The reset circuit (12) has a bridge configuration transistor (
13) and (14) and diodes (15) and (1
6) and is connected to the reset power supply 7).

In addition, each reset circuit (12^), (12B) and (12
) in the diode (15^), (15B), (15),
(16^), (16B), and (16) can also be configured with transistors.

Also, here, the anode reactor (8^) and (8B
), the series circuit including the auxiliary semiconductor element (9) and the auxiliary reactor (10) is provided in common, but it may be provided separately for each.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be explained. In this case, the semiconductor element (4
^) and (4B), and auxiliary semiconductor element (9^),
It is assumed that (9B) and (9) are GTOs, the load connected to the output terminal T is an inductive load, and the load current I is flowing in the direction of the arrow. It is also assumed that the magnitude and direction of the load current I are constant during the switching operations of the semiconductor elements (4^) and (4B).

First, while referring to the waveform diagram in FIG.
The commutation operation of the load current I from the anode reactor (8^) to (8B) and the energy regeneration operation of the capacitor (IB) and the anode reactor (8^) when the anode reactor (8^) is turned off will be explained.

Semiconductor element (4^) is on, semiconductor element (4B), (9
), (9^), and (9B) are off, and the load current ■ is flowing from the DC power supply (6) to the anode reactor (8
^), the electric current of the anode reactor (8^) via the semiconductor element (4^) and the output terminal T.
), the voltage V of the capacitor (1^)
1 a is 0.

Also, if the ratio between the secondary winding and the primary winding of the transformer (3) is n, then the voltage VB of the capacitor (IB>) is charged to a voltage E + E / n higher than the power supply voltage E by E / n. Furthermore, if the auxiliary reactor (10) has a non-negligible inductance value, it is charged to a voltage slightly higher than E + E/n (see FIG. 2).

Here, at time t0, the reset circuit (12), (
12^) and (12B) are not operating, turn off the semiconductor element (4^) and at the same time turn off the auxiliary semiconductor element (9).
When B) and (9) are turned on, the load current I is bypassed to the diode (2^) and capacitor (1^). Therefore, the voltage V I A of the capacitor (1^) is charged by the load current I to the voltage E + E / n.

At this time, the capacitor (IB) and the auxiliary reactor (I
OB) resonates, the energy stored in the capacitor (IB) becomes a regenerative current of 1 gm flowing to the auxiliary semiconductor element (9B), and is transferred to the DC power supply (6) via the transformer (3B) and diode (7B). ) In FIG. 2, the regenerative current I□ is expressed as a negative value.

This regenerative current Ill is generated when the capacitor (IB) completes discharging and the voltage V1. When becomes 0, that is, it becomes a minimum near time t1. After that, the auxiliary reactor (I
Due to the energy stored in OB), regenerative current ■1. continues to flow and becomes 0 when the energy regeneration of the auxiliary reactor (IOB) is completed.

On the other hand, at time t, the voltage of capacitor (1^) ■
When 1^ is charged above the power supply voltage E, a current I flows through the anode reactor (8B). begins to flow.

Subsequently, at time t2, the electric current F of the capacitor (1^)
When E v +^ is filled to more than E0E/n, anno-
The energy stored in the triacdle (8^) causes the anode reactor (8B), auxiliary reactor (10),
A regenerative current I9 begins to flow in the energy release path consisting of the negative winding of the transformer (3), the auxiliary semiconductor element (9), and the anode reactor (8^).

This regenerative current ■ flows through the auxiliary reactor (9).

As a result, the energy stored in the anode reactor (8^) is transferred to I via the transformer (3) and diode (7).
, and is regenerated to the DC power supply (6).

The regenerative current ■, reaches its maximum at time t, and at time t,
The value of the regenerative current I after that is the anode reactor (8^
) Current flowing through 1. It becomes equal to the value of A. Also, time t2
From t, the voltage V I of the capacitor (1^)
A is the rate of increase of the regenerative current ■, and the auxiliary reactor (10
) is further charged by a voltage determined by

In this way, at time t, the anode reactor (8
When the energy regeneration of ＾) is completed, the value of the current IIA of the anode reactor (8＾) becomes O, the value of the current Iss of the anode reactor (8B) becomes the load current I, and the value of the current Iss of the anode reactor (8＾) becomes the load current I, and the value of the current I ) is completed.

Note that during the energy regeneration of the capacitor (IB) by the regeneration current I 9m and the energy regeneration of the anode reactor (8A) by the regeneration flow I, that is, each transformer (3
B) and (3) - During the period when current is flowing through the secondary winding,
The voltage polarity of the secondary winding of each transformer (3B) and (3) is
The side marked with a dot in FIG. 1 is positive.

When the energy regeneration of the capacitor (IB) and the anode reactor (8^) is completed, the auxiliary semiconductor elements (9B) and (9) in each series circuit are turned off. Also, by turning on the transistors (13B), (14B), (13) and (14), the reset circuits (12B) and (12
) to reset volume! ! (11B) and (11), voltages of polarity such that the side without a dot is positive are applied, respectively.

At this time, the reset circuits (12B) and (12) operate the reset windings (11B) and (12) so as to cancel the magnetic flux of the secondary windings of the transformers (3B) and (3) generated during regeneration.
1) Excite.

This induces in the secondary windings of each transformer (3B) and (3) a reset voltage with a positive polarity on the side without a dot. This reset voltage is the reset voltage, respectively! 1 (IIB) and (11) and transformer (3B)
and (3), the iron cores of each transformer (3B) and (3) can be reset faster than self-resetting.

In addition, the magnitude of the reset current is sufficient for the excitation current,
Power consumption is extremely small, and auxiliary semiconductor elements (
Since transformer (3B) and (9) are turned off, transformer (3B
) and (3), no voltage is induced on the − secondary winding side, and no charging path to the capacitor (IB) is formed.
Furthermore, since the diodes (7B) and (7) block the current, no current flows to the secondary windings of the transformers (3B) and (3). ) during energy regeneration via reset winding! An induced current also tries to flow in the dot direction in (IIB) and (11), but since each transistor in the reset circuit (12B) and (12) is turned off, it is blocked by the diode in the reset circuit. The induced current in reset windings II (IIB) and (11) is blocked.

When the reset of each transformer (3B) and (3) is completed,
Transistors (13B), (14B), (13) and (
14) by turning off the reset circuit (12B).
and (12) are each reset winding (IIB) and (11
). The above reset operation allows the regenerative transformers (3B) and (3) to always return to a constant magnetic flux level. In this way, the anode reactor (8^) when the semiconductor element (4^) is turned off
) to the anode reactor (8B) is completed.

Next, while referring to the waveform diagram in FIG.
The commutation operation of the load current I from the anode reactor (8B) to (8^) and the energy regeneration operation of the capacitor (IA) and the anode reactor (8B) when the anode reactor (8B) is turned on will be described.

In this case, the initial state is the state in which commutation from the anode reactor (8^) to (8B) is completed when the semiconductor element (4^) is turned off as described above. At this time, the load current is a diode (5B) and an anode reactor (
8B), the current I of the anode reactor (8B)
It is flowing as sm.

Now, time t. When the semiconductor element (4^) is turned on and the auxiliary semiconductor elements (9) and (9^) are turned on at the same time, the energy stored in the capacitor (1^) is transferred to the auxiliary reactor (IOA).

At this time, the discharge current of the capacitor (1^) flows to the negative winding of the transformer (3^) as a regenerative current I9A flowing to the auxiliary reactor (9^). As a result, the energy stored in the capacitor (1^) is transferred to the transformer (3^).
DC power supply (
6) is regenerated.

At time 1+□, the voltage V I of the capacitor (1^)
Even if A becomes 0 and the discharge of the capacitor (1^) is completed, the auxiliary reactor (IOA) is connected to the diode (5^).
, (2^), auxiliary semiconductor element (9^) and transformer (3^
) Continue to flow the regeneration through the path consisting of the next winding. Thereby, the energy stored in the auxiliary reactor (IOA) is regenerated to the DC power supply (6) via the secondary winding of the transformer (3^) and the diode (7^). That is,
All the energy stored in the capacitor (1^) will be regenerated.

Also, at time tl+, the current flowing through the semiconductor element (4^), that is, the current I@ of the anode reactor (8^) reaches the load electric lacquer, and the current flowing through the diode (5B), that is, the current of the anode reactor (8B). The current 1@ll becomes O.

After that, the current ■8A flowing through the semiconductor element (4^) further increases, and the current of load current 1 or more is bypassed to the diode (2B) and capacitor (IB) on the parallel snubber circuit B side, and the capacitor (IB); The voltage V 1 ll begins to be charged.

Moreover, after time 1, the current Ism flowing through the anode reactor (8B) is equal to the current 1 of the anode reactor (8^).
When the voltage V 1 B of the capacitor (IB) reaches the power supply voltage E at time 0 t, which increases in the negative direction symmetrically with 1A, = t'Fir and 8. Both reach extreme values and begin to decrease.

At time t14, when the voltage V of the capacitor (IB) is charged to the voltage E + E / n or more, the energy stored in the anode reactor (8^) and (8B) causes the anode reactor (8B) and the auxiliary The regenerative electric lacquer flows through a path consisting of the reactor (10), the secondary winding of the transformer (3), the auxiliary semiconductor element (9), and the anode reactor (9^). As a result, the energy stored in the anode reactor (8^) and (8B) is
It is regenerated to the DC power supply (6) via the secondary winding of the transformer (3) and the diode (7).

The regenerative current I, reaches its maximum at time t15, and at time t
The value of the regenerative current I after 15 is the anode reactor (
8＾) Current flowing through■. is equal to the value of Also, time t
, at t's, the current V in the capacitor (IB)
IB is the rate of increase of regenerative electric lacquer work and the auxiliary reactor (
10) is further charged by the voltage determined by 10).

At time t4, the anode reactor (8^) and (
When the regeneration of the anode reactor (8B) is completed, the anode reactor (8B)
) to (8^) is completed.

In addition, while the energy regeneration of the capacitor (1^) by the regenerative tfCI-A and the energy regeneration of the anode reactor (8^) and (8B) by the regenerative electric lacquer work are being performed, that is, the regeneration transformer During the period when current is flowing through the secondary windings of (3A) and (3), the voltage polarity of the secondary winding of each transformer (3^) and (3) is indicated by the dot in Figure 1. The side that did so is correct.

When the energy regeneration of the capacitor (1^), anode reactor (8^) and (8B) is completed, each auxiliary semiconductor element (9^) and (9) is turned off, and the transistors (13^) and (14^) are turned off. ), (13) and (14), and from the reset circuits (12^) and (12) to the reset windings l1 (11^) and (11), set the polarity such that the side without a dot is positive. Apply a voltage of This induces a reset voltage in the secondary windings of the transformers (38) and (3), each of which has a positive polarity on the side without a dot.

This reset voltage is applied to each reset winding (IIA) and (
11) and the ratio of the secondary windings of each transformer (3^) and (3), so the iron cores of transformers (3^) and (3) can be reset faster than when self-resetting. can do. When the reset of each transformer (3^) and (3) is completed, the transistors (13^) and (14^)
, (13) and (14) are turned off, and the reset circuit (1
2A) and (12) to the reset winding (11A) and (
The magnetic flux level of the transformer (3^) and (3) can always be returned to a constant level by a reset operation of 0 or more that stops the voltage application to the transformer (3^) and (3). In this way, the commutation of the load current ■ from the anode reactor (8B) to (8^) is completed.

Incidentally, if the load flow (2) is flowing in the opposite direction to the arrow, the situation is completely symmetrical to that described above. That is, by turning off the semiconductor element (4B), commutation is performed from the anode reactor (8B) to (8^), and by turning on the semiconductor element (4B), the commutation is performed from the anode reactor (8^). (
8B) is carried out.

In this way, the capacitor (1^) in each parallel snubber circuit
and (IB) and anode reactor (8^) and (
By regenerating all the energy stored in 8B),
Achieves higher efficiency in power conversion equipment. In addition, reliability is improved by energizing the reset windings (11A), (11B), and (11) to reset the transformers (3^), (3B), and (3) quickly and reliably. In addition, in the above embodiment, the series circuit for energy regeneration of the capacitor (1^) and (IB) in each parallel snubber circuit is replaced by the capacitor (1^) and (IB). ), but
The series circuit for energy regeneration consists of a capacitor (1^) and (
It may be connected to other locations as long as it is provided in the discharge path of IB).

FIG. 4 is a circuit diagram representatively showing another configuration example of one parallel snubber circuit, and shows a case where the discharge path of the capacitor (1^) is formed in parallel with the diode (2Δ). In this case, a series circuit consisting of the negative winding of the transformer (3^), the auxiliary semiconductor element (9^) and the auxiliary reactor (IOA) is connected across the diode (2^).

Also, although the case where the anode reactors (8^) and (8B) are connected to both sides of the output terminal T is shown, they may be inserted at any position, such as the positive side or the negative side of the DC bus. In this case, a series circuit for energy regeneration of each anode reactor (8^) and (8B) will be provided individually.

Also, in order to reset the transformers (3^) and (3B), separate reset windings (11^) and (IIB> and reset circuits (12^) and (12B) were provided, but the transformers ( The secondary windings of 3^) and (3B) may be shared, and one reset winding and reset circuit may be provided for each. In this case, together with the transformer, reset winding, and reset circuit, the diode (7^) and (7B) can also be shared by one diode, making it possible to further reduce the size.

In addition, each reset circuit (12A), (12B) and (12
), the reset power supply (17) for the transformers (3), (38), and (3B) can be reliably prevented from saturation. Therefore, it can be easily applied to large-capacity power converters suitable for linear motors and the like.

FIG. 5 is a circuit diagram showing another embodiment when applied to a large-capacity power conversion device, in which a plurality of semiconductor elements (4^) and (4B) are connected in series between the DC buses, respectively. It has been inserted. In this case, there are nine pairs of transformers (3
Reset volume corresponding to ^) and (38)! (11A
) and (11B> are commonly connected in series for each arm.

Furthermore, as shown in FIG. 6, it can also be applied to power converters such as through-level inverters.

Here, only one unit on the positive side of the DC bus of the power converter when the capacity is increased is representatively shown. In this case, the series snubber circuit, i.e. the anode reactor (88)
is divided, but reset volume! ! By connecting (11) in series and sharing the reset circuit (12),
It is possible to prevent the device from increasing in size.

[Effects of the Invention] As described above, according to the present invention, the discharge path of the capacitor includes an auxiliary semiconductor element that is controlled in synchronization with the semiconductor element, and an auxiliary semiconductor element that protects the auxiliary semiconductor element and makes it resonate with the capacitor. A series circuit consisting of the reactor and the primary winding of the transformer is provided, and an auxiliary semiconductor element controlled in synchronization with the semiconductor element and an auxiliary semiconductor element for protecting the auxiliary semiconductor element are provided in the energy release path of the anode reactor. A series circuit consisting of a reactor and the primary winding of the transformer is provided, the secondary winding of each transformer is inserted between the DC buses, and a plurality of reset windings are individually magnetically coupled to each transformer. wire and a plurality of reset circuits for energizing each reset winding in a direction that cancels out the magnetic flux of the secondary windings, so that the energy stored in the series snubber or anode reactor as well as the capacitor in the parallel snubber circuit is Since the snubber circuit is also regenerated, it is possible to obtain a snubber circuit that realizes high efficiency of the power conversion device.

In addition, the excitation of the reset winding cancels out the magnetic flux on the secondary winding side of the transformer and prevents saturation of the iron core, reducing the reset time of the transformer and improving reliability.
It has the effect of providing a snubber circuit that realizes higher frequencies in power converters.Furthermore, by applying it to power converters in which multiple pairs of semiconductor elements are connected in series and inserted between DC busbars, large capacity has been achieved. This has the effect of providing a snubber circuit.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention together with a power conversion device, Figs. 2 and 3 are waveform diagrams for explaining the energy regeneration operation of Fig. 1, and Fig. 4 is applied to the present invention. Fig. 5 is a circuit diagram showing an embodiment of the present invention applied to a large-capacity power converter, and Fig. 6 is a circuit diagram showing another example of the configuration of a parallel snubber circuit applied to a through-level inverter. FIG. 7 is a circuit diagram showing a conventional snubber circuit together with a power conversion device. A, B...Parallel snubber circuit (1 person), (IB)...Capacitor (2^), (2B)...Diode (3^), (3B), (3)...Transformer (4^), (
4B)...Semiconductor element (8^), (8B)...Anode reactor (9^)
, (9B), (9)...auxiliary semiconductor element (10^),
(IOB), (10)...Auxiliary reactor (11^)
, (IIB), (11)...Reset winding (12^)
, (12B), (12)...In the reset circuit, the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A snubber circuit provided for multiple pairs of semiconductor elements inserted between DC buses of a power converter, comprising: a capacitor connected in parallel to each of the semiconductor elements, and charging of the capacitor. a parallel snubber circuit including a diode connected in the direction of the semiconductor element for suppressing a rate of increase in the voltage applied to the semiconductor element; and an anode reactor connected in series to each pair of the semiconductor elements, the circuit comprising: A snubber circuit comprising a series snubber circuit that suppresses the rate of increase in the supplied current, wherein the discharge path of the capacitor includes an auxiliary semiconductor element that is controlled in synchronization with the semiconductor element, and a series snubber circuit that protects the auxiliary semiconductor element. Further, a series circuit consisting of an auxiliary reactor for resonance with the capacitor and a primary winding of the transformer is provided, and an auxiliary semiconductor element controlled in synchronization with the semiconductor element is provided in the energy release path of the anode reactor. , a series circuit consisting of an auxiliary reactor for protecting this auxiliary semiconductor element and a primary winding of a transformer is provided, a secondary winding of each of the transformers is inserted between the DC buses, and each of the transformers a plurality of reset windings individually magnetically coupled to the device; and a plurality of reset circuits for exciting each of the reset windings in a direction that cancels the magnetic flux of the secondary winding. Features a snubber circuit.